This invention relates generally to the manufacture of structural members, such as I-beams, and more particularly to continuous, extremely long, light-weight members. The invention has particular application in the manufacture of plastic and fiber-reinforced composite plastic shapes.
With the advent of earth to orbit transportation in outer space, mission operations will change from one-purpose to continuous operations embracing a wide spectrum of applications. These operations introduce a new dimension in space structures, particularly in such applications as communications, microwave radiometry and power generation. Permanent space platforms, providing common structural and operational support for a variety of space systems, will be extremely large requiring structural members measuring thousands of feet in length.
Prior work on space structures has concentrated on modular metallic structures pre-assembled in volume-consuming packages to fit within the limitations of the space craft's payload volume. To utilize these modules in space to fabricate a large structure requires extensive Extra-Vehicular Activity (EVA) efforts of space crewmen.
The geometry of large light-weight structures in space is dynamicly disturbed by control forces imposed for orientation and positioning of the system. Also, absorbed thermal radiation causes distortion and changes in length of the structural members. The distortion of the structure due to control forces is minimized by the use of high stiffness materials that have low density to reduce mass moments of inertia, which thereby reduce the control forces. Thus it may be appreciated that the ideal material would be one having zero thermal expansion, high elastic modulus, high strength, and low density.
When graphite/plastic composites are compared with aluminum, titanium, steel, invar, and beryllium, the composites are far superior in the characteristics desired. Beryllium is the only metal almost as stiff as the composites, but in thermal distortion the composites are as much as fifty times better than beryllium.
In the disclosed invention prepreg fiber-reinforced plastic tape is fed from reels into an apparatus to form the tape into a consolidated structural shape, such as a laminated strip, angle or channel to provide a continuous member of any lengths desired. The compact apparatus occupies only a fraction of the space required for pre-fabricated components. Complexity of large space structures and their assembly in space is substantially reduced due to the elimination of joints required for the sole purpose of fitting pre-assembled structure modules into the payload volume.
Thus it can be seen that the disclosed invention produces structural members which greatly simplify a deployed space structure, substantially reduce EVA, and with compact storage greatly reduce the number of earth-to-orbit flights required for placement of the space structure. Such structually efficient members clearly have utility on earth, such as for example in solar energy collecting devices, large antenna and other structures where low thermal distortion and high strengths-to-weight properties are required.